This invention relates to a filter bag having a protective cuff or skirt which protects the "free" end portion of the filter bag opposite the end mounted to an apertured plenum chamber plate from abrasion damage and the like.
Filter bags are commonly used in dust collectors to remove dust and other particulate matter from dirty air before being exhausted into the atmosphere. These filter bags are mounted in bag houses conventionally having from 4 to several thousand filter bags mounted to an apertured plenum chamber plate. The filter bags may be of any desired length but conventionally they may be from 6 to 20 feet in length.
The filter bags having a protective cuff according to the present invention have particular value in a multiple filter bag collector which employs pulse jet cleaning techniques for cleaning the elongate tubular filter bags. Cleaning of the filter bags in these bag houses is effected by the abrupt and momentary introduction of a high energy pulse of air or gas into the interior of the filter bag. Such a pulse produces a momentary pressure differential countercurrent to that extant during normal filter flow causing the dislodgement of accumulated dust particles from the outer wall of the filter bag. It is common in this type of bag house for the filter bag assemblies including the filter bags and associated retainers to strike and rub against one another and against the bag house housing thereby abrading the filter bag material which eventually renders the filter bags ineffective.
Bag houses may be of the top mounted filter bag or bottom mounted filter bag type. A top mounted filter bag has the filter bags depending from the apertured plenum chamber plate or tube sheet. When a filter bag must be replaced, the filter bag with the supporting retainer is removed from the tube sheet and the old filter bag is taken off the retainer and replaced with a new filter bag. The retainer with the new filter bag is then reinserted through the tube sheet and the retainer and filter bag are secured in place.
Each tubular filter bag has an open end mounted to the tube sheet covering an aperture in the tube sheet. The other end is closed and is referred to herein as the "free" end. This closed end has an end piece, which when the filter bas has a circular cross-section is a disc element, sewn circumferentially to the wall of the filter bag to close this end of the filter bag.
In conventional bag houses, the spacing between bags is approximately 21/2 inches. In top removal bag houses the workers who replace filter bags cannot observe and adjust the position of the filter bag assemblies when the retainer with filter bag is reinserted through the tube sheet after replacement of the filter bag. In the case of a 12 foot long filter bag which is positioned axially one degree out of plumb, the deflection at the bottom is 21/2 inches, which as noted above, is the conventional spacing of filter bags in a bag house. When retainers of adjacent filter bag assemblies strike each other during normal pulse jet cleaning, the retainers have a tendancy to cut the filter bag material at the "free" ends of the filter bag and abrade the stitching of the end piece to the filter bag wall.
In addition to the above described mechanical abrasion, the stitching of the closed end may be subjected to areodynamic abrasion caused by the inlet dirty air, carrying particulate matter, striking the end wall of the filter bag when dirty air is forced into the bag house under pressure. The velocity of the dirty air may be such to cause substantial wear to the stitching at the closed end. The protective cuff contemplated by the present invention provides protection from this condition.